Define stimulus transduction.

The process by which a sensory receptor converts the sensory stimulus into an electrical signal that is carried by sensory axons

2

What is a graded potential (aka generator potential or receptor potential)?

-changes in ion fluxes across the membrane in varying degrees (not all or none)-an increase in magnitude of a receptor potential (stimulus energy) causes an increase in frequency of action potentials

3

Define adaptation or desensitization.

-decrease in frequency of action potentials in a sensory neuron despite maintenance of the stimulus at constant strength

4

What is the difference between rapidly adapting (phasic) receptors and slowly adapting (tonic) receptors?

-rapidly adapting: response quickly to onset of stimulus then decreases over time or may stop responding. important for indicating change in stimulus. E.g. putting on a sock, then forgetting it is on your feet-slowly adapting: responses that maintain response to stimulus over time, e.g. receptors in joints/muscles that convey positional info, receptors that measure oxygen tension in blood

What are the 4 attributes coded for by a sensory stimulus?

How do receptive fields of neurons convey the degree of acuity of a particular sense?

-overlapping receptive fields give more precise location (e.g. if recorded by 3 neurons, stimulus is at the intersection of those receptive fields)-size of receptive field: small on fingertips and large on back (less able to distinguish between two points close together) [2 point discrimination]-lateral inhibition: ability of excited neuron to reduce activity of it neighbors and sharpen spatial profile of excitation

7

Where is neuron 1 and its axons for the DC/ML pathway?

Neuron 1 is in DRGIts axons for C1-T5 are in Fasciculus cuneatus in spinal cordIts axons for T6-S5 are in Fasciculus gracilis in the spinal cord

8

Where is neuron 2 and its axons for the DC/ML pathway? Where is neuron 3?

Neuron 2 is the Nucleus cuneatus and Nucleus gracilis in the lower medulla. Its axons take the ML pathway after decussation. Neuron 3 is VPL in the thalamus.

9

Where is neuron 1 and its axons for the STT pathway?

Neuron 1 is DRGIts axons doesn't have a name

10

Where is neuron 2 and its axons for the STT pathway? Where is neuron 3?

Neuron 2 is nucleus proprius in the dorsal horn where the axons of neuron 1 enter the spinal cord. Axons of neuron decussate 1-2 segments above nucleus proprius through white commissure and follow STT tract to Neuron 3-VPL in thalamus

11

Where is neuron 1 and its axons for the TL (trigeminal lemniscus) pathway?

Neuron 1: trigeminal ganglionIts axons aren't named

12

Where is neuron 2 and its axons for the TL pathway? Where is neuron 3?

What are the features of isolated peripheral nerve lesion (mononeuropathy)?

-Sensory: numbness and loss of light touch, pinprick, and vibration sense in a targeted dermatome or area of an individual limb or trunk dermatome-motor: weakness or loss of limb or digit movements, possible atrophy of muscle. decreased deep tendon reflex-common causes: contusion, crush, or laceration of a ventral rams of a peripheral nerve

20

What are the features of distal symmetrical polyneuropathy? [degeneration of distal axons]

What are the features of a central cord syndrome (springomyelia-small lesion)?

-Sensory: segmental loss of pain and temperature bilaterally at the level of lesion. Lose crossing fibers in 1-2 segments (STT)-motor: only occur with larger lesion that effects the anterior horns of spinal cord-common causes: central cavitation can be congenital or acquired due to trauma, tumor, etc.

What are the features of a primary sensory cortex or thalamic lesion?

-contralateral sensory deficits of all sensory modalities to parts of the body or face dependent on the size of the injury (think of the person lying over the lobe of the brain)-lesions of parietal lobe: contralteral deficits in higher order sensory processing-lesions of parietal lobe on the left: contralteral hemineglect